Implant, more particularly partial ulnar head implant

Abstract

A method and apparatus for replacing an articular surface of a bone. The implant includes at least one head with a bore and a lateral articular surface generally perpendicular to an axis of the bore. A holding element includes a stem at a proximal end adapted to attach to the bone. A member at a distal end of the holding device is adapted to engage with the bore in the head so that the lateral articular surface is positioned to engage transverse loads. The bore permits limited lateral translation of the head in at least one direction generally perpendicular to a longitudinal axis of the member.

1. An implant comprising:
 a head adapted to replace at least a lateral articular segment of a bone taking up transverse loads, the head having a lateral articular surface, the lateral articular surface formed by an outer surface of the head that is adapted to withstand the transverse loads, the head further having an engagement surface generally opposite the lateral articular surface that is adapted to engage with a non-resected portion of the bone; and 
 a holding element connected with the head that is adapted to be fastened to the bone, wherein the head is mobile in translation relative to the holding element in at least one direction that corresponds to a direction of the transverse loads when the implant is in place in the patient. 
 
     
     
       2. The implant of  claim 1  wherein the lateral articular surface comprises pyrocarbon. 
     
     
       3. The implant of  claim 1  wherein the head comprises pyrocarbon. 
     
     
       4. The implant of  claim 1  wherein the implant comprises an ulnar head implant. 
     
     
       5. The implant of  claim 1  wherein the implant comprises a partial ulnar head implant and the articular surface engages with a radial head. 
     
     
       6. The implant of  claim 1  wherein the implant comprises a partial ulnar head implant and the head is retained to the member solely by a triangular ligament. 
     
     
       7. The implant of  claim 1  comprising a plurality of heads in which a distance from the axis of the bore to the lateral articular surface varies in at least two heads. 
     
     
       8. The implant of  claim 1  comprising a plurality of heads in which a shape of the lateral articular surface varies in at least two heads. 
     
     
       9. An implant to replace a resected articular surface of a partially resected head of a bone, the implant comprising:
 a holding element comprising a stem at a proximal end adapted to attach to the bone and a member at a distal end; and 
 a head comprising a bore adapted to engage with the member, a lateral articular surface generally perpendicular to an axis of the bore formed by an outer portion of the head, and positioned generally at the location of the resected articular surface, and a surface on the head generally opposite the lateral articular surface and adapted to engage with a non-resected portion of the head, wherein the bore permits limited lateral translation of the head in at least one direction generally perpendicular to a longitudinal axis of the member in response to transverse loads. 
 
     
     
       10. The implant of  claim 9  wherein the head comprises a generally lateral planar face generally perpendicular to the axis of the bore and opposite the lateral articular surface. 
     
     
       11. The implant of  claim 9  wherein the bore comprises a generally circular cross section and the member comprises a cylindrical pin, wherein the circular cross section of the bore has a diameter greater than a diameter of the cylindrical pin. 
     
     
       12. The implant of  claim 9  wherein the bore comprises a cross-sectional area greater than a cross-sectional area of the member. 
     
     
       13. The implant of  claim 9  wherein the bore permits lateral translation of the head in any direction generally perpendicular to the longitudinal axis of the member. 
     
     
       14. The implant of  claim 9  wherein the lateral articular surface comprises pyrocarbon. 
     
     
       15. The implant of  claim 9  wherein the head comprises pyrocarbon. 
     
     
       16. The implant of  claim 9  wherein the stem comprises an elastically deformable material. 
     
     
       17. The implant of  claim 9  wherein the implant comprises an ulnar head implant. 
     
     
       18. The implant of  claim 9  wherein the implant comprises a partial ulnar head implant and the articular surface engages with a radial head. 
     
     
       19. The implant of  claim 9  wherein the implant comprises a partial ulnar head implant and the head is retained to the member solely by a triangular ligament. 
     
     
       20. The implant of  claim 9  wherein the stern and the longitudinal axis of the member are adapted to be oriented generally parallel to the bone. 
     
     
       21. The implant of  claim 9  comprising a plurality of heads in which a distance from the axis of the bore to the lateral articular surface varies in at least two heads. 
     
     
       22. The implant of  claim 9  comprising a plurality of heads in which a shape of the lateral articular surface varies in at least two heads. 
     
     
       23. An implant to replace an articular surface of a bone, the implant comprising:
 a plurality of heads in which a distance from the axis of the bore to the lateral articular surface varies in at least two heads, the plurality of heads including at least one head comprising an inner bore and an outwardly facing lateral articular surface generally perpendicular to an axis of the bore; and 
 a holding element comprising a stem at a proximal end adapted to attach to the bone and a member at a distal end adapted to engage with the bore in the head, the member positioning the lateral articular surface to withstand transverse loads, the bore permitting limited lateral translation of the head in at least one direction generally perpendicular to a longitudinal axis of the member. 
 
     
     
       24. An implant to replace an articular surface of a bone, the implant comprising:
 a plurality of heads in which a shape of the lateral articular surface varies in at least two heads, the plurality of heads including at least one head comprising an inner bore and an outwardly facing lateral articular surface generally perpendicular to an axis of the bore; and 
 a holding element comprising a stem at a proximal end adapted to attach to the bone and a member at a distal end adapted to engage with the bore in the head, the member positioning the lateral articular surface to withstand transverse loads, the bore permitting limited lateral translation of the head in at least one direction generally perpendicular to a longitudinal axis of the member.